ABSTRACT! Kaposi's sarcoma (KS) remains a highly prevalent malignancy in sub-Saharan Africa. Antiretroviral therapy (ART) and associated immune reconstitution has been correlated with a dramatic decline in the prevalence of KS in the US HIV infected population, but the impact of ART on KS in sub-Saharan Africa is less clear. In Zambia, even with the scale up of ART, KS remains the second most common cancer among adult men. For women, it is the third most common. Furthermore, treatment with chemotherapy plus ART is associated with recurrence rates of up to 50 percent in those that have a complete response. The overall objective of this application is to identify markers of epidemic KS recurrence and/or sustained remission in individuals that have an initial complete regression of lesions upon chemotherapy. We hypothesize that individuals with complete regression of all the lesions after chemotherapy will have differences in immunological and viral factors that have prognostic value for predicting KS re-development and/or sustained remission. We will test our hypothesis by longitudinally characterizing innate, humoral, and cellular immune responses against KSHV and comparing individuals that experience recurrence to those who do not. The identification of these biomarkers of outcome after remission will enable the selection of patients that require a longer follow up period, those that require maintenance therapy, and those that require second line chemotherapy. From our proposed activities, we will improve the long-term outcomes of HIV+ individuals that have had KS before and hence at high risk of recurrence. This will ultimately inform efforts to better understand KS pathogenesis and develop novel interventional strategies.